How to Skim Coat Walls

A new approach for smoothing rough walls that's easy to master

Smooth over rough or damaged walls with a skim coat of mud, applied with a special squeegee knife. It's easy to do and delivers great results.

By the DIY experts of The Family Handyman Magazine

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Overview: The method and key tools

If you’re a skilled drywall taper or plasterer, you probably use a hawk and trowel to skim-coat walls. We don’t expect to change your mind if you use those tools as second hands. But if you’re a remodeler who does only occasional skim-coating to fix wrecked walls, you know it’s a tough skill to master.

The method we show isn’t faster than traditional skim-coating—you have to do two or three coats and let each one dry in-between. But it’s idiot-proof, and the walls will end up flat and smooth. So if you’re a contractor who’s given up on skim-coating and you always call in a taper for the task, you can save on labor by tackling it yourself next time. It only takes a regular paint roller and a squeegee knife. The 14-in.-wide squeegee knife we used is called a Magic Trowel. It costs about $25 and is available at some Sherwin-Williams stores. To find online sources, search for “TexMaster 9927” or “squeegee knife.”

Step 1: Start by prepping the walls

Photo 1: Prime the walls

Roll a fast-drying, stain-sealing drywall primer on the walls. The primer seals loose paper and promotes better adhesion of the joint compound.

With this method, you don’t just spot-prime; you roll the entire wall with a stain-blocking sealer (Photo 1). If you’ve always used solvent-based sealers like traditional BIN and KILZ, it’s time to try one of the water-based stain killers. Zinsser’s Bulls Eye 1-2-3 primer works well, and you won’t have any whining from your customers about the smell. But don’t rush on to the next step; let the sealer dry thoroughly before applying any joint compound.

These are thin layers that won’t fix holes or torn-away paper, or make uneven sections level. Patch these problems with setting-type joint compound. Let the compound harden (it doesn’t have to be dry) before you start skimcoating.

Step 2: Roll on the mud

Photo 2: Roll on the mud

Spread a layer of slightly thinned all-purpose joint compound on the walls with a heavy-nap roller. Work in small sections so you can smooth out the joint compound before it starts to dry.

Mix all-purpose joint compound to about the same consistency as mud you’d use for bedding tape (the consistency of mayonnaise, or just thin enough to roll on the wall). You’ll get shrinkage if you mix it too wet. Don’t worry if you get cracking on the first coat; just mix the next coat a little thicker by spooning in some fresh mud from another bucket.

Use a 1/2-in.-nap roller to roll mud on an area about 4 ft. square (Photo 2). Try to keep it as even as you can so the squeegee work will go better for you.

Step 3: Wipe it smooth

Photo 3: Trowel the first coat

Smooth the joint compound with the squeegee knife. Start in the top corner and pull down.

Photo 4: Pull up from the bottom

Roll joint compound onto the lower section and smooth it by pulling the trowel upward.

Photo 5: Scrape off lumps

Scrape the wall with a 6-in. putty knife to remove lumps and ridges. Brush off the wall and you’re ready for the next coat.

Smooth the mud with the squeegee knife. Keep a damp rag and a mud pan handy. Use the rag to wipe the blade after every few strokes and the mud pan to wipe off excess mud that builds up on the blade. Starting at the top corner, set the squeegee knife against the wall and pull it down (Photo 3). Overlap each vertical pass until you finish the section.

You may have to go over some areas a few times. It won’t take you long to get the hang of using the squeegee knife. When you’re done with the top section, roll joint compound on the lower half. Pull the squeegee knife from the bottom up (Photo 4). Touch up along the edges as you go.

Let the first coat of joint compound dry. To speed up drying time, especially if the air is humid, bring a space heater and a box fan or two. You don’t have to sand between coats; just knock off lumps or proud mud lines with a 5- or 6-in. putty knife to avoid streaks in the next coat (Photo 5).

Step 4: Apply one or two more layers

Photo 6: Change directions for the second coat

Trowel the second coat horizontally. If you still see indentations or imperfections after the second coat dries, trowel on a third coat.

It sounds like a lot of work to apply two or three coats of joint compound, but the process is quick and the thin layers dry fast. As you know, the smoother you get the wall, the less sanding you’ll get stuck with. Trowel off each successive layer at a right angle to the previous one. After the last coat dries, pole-sand the wall with 120-grit paper. If you have too many peaks and valleys, hit the walls with 100-grit first.

Tip: Give this squeegee-like taping knife a shot for smoothing out tape joints next time you tape. It tapers the edges and you’ll have no trowel or taping knife marks.

Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

4-in-1 screwdriver

Mud pan

Paint roller

Paintbrush

Roller sleeve, 1/2-in. nap

Safety glasses

Sanding pole

Squeegee knife, 14-in. wide

Taping knife

Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here’s a list.